In general, a high quality packaging material is one that creates a good oxygen and moisture barrier. Packaged goods are intended to last longer typically by reducing their interaction with oxygen and water, which usually can deteriorate the product causing waste and other problems. Polymeric materials are often used as packaging materials because they create a good oxygen/moisture barrier and their appearance and shape can be easily controlled. Plastic materials are also used in place of glass for bottling because they are lighter, are more resistant to breakage when dropped, and can be less expensive. Several common polymeric materials used for packaging are polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC), and polystyrene (PS).
Polystyrene is one of the largest volume thermoplastic resins in commercial production today. It is a hydrocarbon chain containing a phenyl group on every other carbon atom. Polystyrene is a durable polymer that is frequently encountered in daily life. A few common examples of polystyrene are plastic toys, computer housings, foam packaging, foam cups, etc.
Injection blow molding (IBM) and injection stretch blow molding (ISBM) are well-developed techniques to produce plastic containers that include the formation of a perform that is subsequently heated and blow molded to produce a hollow container. Preforms are generally condensed shapes, which may include relatively thick-walled tube shaped articles having a threaded neck to facilitate appropriate closure. The preforms can be blown into a desired article shape by heating, stretching, and blowing the preform with a compressed gas. The compressed gas expands the preform into the shape of the mold.
Polymer nanocomposites comprise polymeric materials and inorganic layered compounds, such as clay. When these inorganic layered components are properly incorporated into a polymer matrix, significant improvements in physical and mechanical properties can be displayed. The extent of uniformity of the layered compound incorporated into the polymer matrix influences the characteristics of the nanocomposite.
A high degree of intercalation (the inserting of a molecule, or group of molecules, between a layer of clays) and exfoliation (the delamination of layered materials into disordered layers or sheets) are desired in order to achieve proper incorporation of the inorganic layered compounds into a polymer matrix. In order to achieve a high degree of intercalation and exfoliation, the clays can be treated by some organic chemicals to increase their surface hydrophobicity and interlayer distances. These clays can be referred to as organoclays.
An initial evaluation of polystyrene for blow molding applications led to shrinkage and warpage issues. It is desirable to have polystyrene compositions that can minimize shrinkage and warpage during blow molding.